Portion of a tractor



FIG. 1 is a front perspective view of a portion of a tractor showing our new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a rear perspective view thereof.

The broken line showing of the tractor is included for the purpose of illustrating environmental structure and forms no part of the claimed design. 

The ornamental design for a portion of a tractor, as shown and described. 